The invention relates to methods for non-invasive detection of ocular pathologies. More particularly, the invention provides a non-invasive method for detecting molecular changes in the eye of a subject that are associated with an ocular pathology. The method can be used for the identification of diabetes-associated molecular changes and the identification of individuals at risk for developing diabetes.
Diabetes mellitus is a complex group of syndromes that have in common a disturbance in the oxidation and utilization of glucose, which is secondary to a malfunction of pancreatic beta cells. One of the most threatening aspects of diabetes mellitus is the development of visual impairment or blindness consequent to cataract formation, retinopathy or glaucoma. Diabetes-related ocular pathologies often go undiagnosed until visual function is compromised.
There is a need for non-invasive methods for prospective identification of individuals at risk for developing diabetes and for identifying ocular pathology in its earliest stages. Non-invasive methods will require techniques which avoid exposing the eye to unsafe light intensities while still producing data capable of detection and analysis. References describing techniques relevant to non-invasive ocular measurements, including Raman spectroscopy, include J. Sebag et al., 1994, Invest. Ophthamol. Vis. Sci., 35(7):2976-2980; Y. Ozaki et al. 1987, Applied Spectroscopy 41(4):597-605; A. Mizuno and Y. Ozaki, 1991, Lens and Eye Toxicity Research, 8:177-187; N. T. Yu and E. J. East, 1975, J. Biol. Chem. 250:2196-2202; N. T. Yu and E. J. East, Current Eye Research, 1(10):615-618; Y. Ozaki et al., 1987, Applied Spectroscopy, 47(7):1245-1247; S. Toshima et al., 1990, Ophthalmol., 344:436-441; A. Mizuno et al., 1990, Exp. Eye. Res., 50:647-49; I. Seibinga et al., 1992, Exp. Eye. Res. 54:759-767; J. P. Wicksted et al., 1995, Appl. Spec., 49:987-993; R. R. Ansari et al., 1996, Ophthalmic Technologies VI, pp. 12-20; R. R. Ansari et al., 1996, Lasers in Ophthalmology III, pp. 62-72; R. R. Ansari; N.J. Bauer et al., 1998, IVOS, 39(5), pp 831-835, and K. I. Suh, 1996, Optical Diagnostics of Living Cells and Biofluids, Vol. 2678.
The invention provides methods for the use of Raman spectroscopy to non-invasively detect molecular characteristics of the constituents of the aqueous humor, vitreous humor, lens or retina. The method can be employed for the detection of molecular changes underlying ocular pathologies. The non-invasive method provided by the invention makes use of techniques and equipment that enable detection of Raman spectra with light intensities that fall within acceptable safety standards.
The methods disclosed herein encompass a variety of embodiments. In one embodiment of the invention, the method involves the steps of introducing light into the eye of the subject using a laser; collecting Raman spectra emitted from the eye; dispersing the collected Raman spectra onto a detector; and analyzing detected Raman spectra to quantify a molecular change related to an ocular pathology. In a preferred embodiment, the method is employed to detect early markers of diabetes or diabetes-induced ocular pathologies. In highly preferred embodiments of the invention, the ocular pathology is a pre-cataract marker or a pre-retinopathy marker. In a variation of this embodiment, the method further involves correlating the Raman spectra with traditional markers associated with known ocular pathologies. In an illustrative embodiment, the markers associated with diabetes induced ocular pathologies include blood glucose and insulin levels.
In other embodiments of the invention, detected Raman spectra obtained from a subject suffering from an ocular pathology is analyzed and compared to a normal spectral pattern in order to identify a molecular change that is associated an ocular pathology. In a specific embodiment of this method, the subject is a sand rat and the ocular pathology is diabetes induced ocular damage. In a related embodiment, Raman spectroscopic measures obtained from a patient can be compared to a data set range of measures established from subjects with normal to severely pathological ocular measures to determine the current status of the subject""s condition.